The death and rebirth of American liberalism both began with flags in Grant Park. On Aug. 28, 1968, 10,000 people gathered there to protest the Democratic Convention taking place a few blocks away, which was about to nominate Lyndon Johnson's Vice President, Hubert Humphrey, thus implicitly ratifying the hated Vietnam War. Chicago mayor Richard Daley had warned the protesters not to disrupt his city and denied them permits to assemble, but they came anyway. All afternoon, the protesters chanted and the police hovered, until about 3:30, when someone climbed a flagpole and began lowering the American...